1. Technical Field of the Invention
The present invention relates to a diversion detection which not only detects a registration diversion between a reticle (a magnified mask) or a full-size mask (hereinafter referred to as a reticle) and a wafer prior to a main exposure but also detects a lithographic magnification error.
2. Description of the Prior Art
Recently, reduction projection exposure apparatus have been used as apparatus for the lithography of microscopic circuit patterns in the manufacture of semiconductor devices such as ICs and LSIs. This reduction projection exposure apparatus is designed so that the circuit pattern formed on a reticle is exposed and printed in a reduced form in the photoresist (photosensitive material) formed on the wafer through a projection lens. While the projection lens has a resolution on the order of 1 micron, even if a projection lens of such high resolution is used, there are cases where a diversion is caused and satisfactory accuracy is not obtained in the registration exposure of the circuit pattern (chip) already formed on the wafer and a projected image of the circuit pattern on the reticle. It is considered that the causes of this diversion include relative run-outs of the circuit pattern (chip) on the wafer and the projected image of the circuit pattern on the reticle due to a run-out of the wafer caused by the processing of the wafer (a process such as etching or diffusion), variations in the reduction magnification of the projection lens itself, a registration diversion between the wafer and the reticle and the like. In the past, the detection of a registration diversion between a wafer and a reticle has been effected by measuring with given measuring means the circuit pattern formed on the wafer through its exposure and development. However, there has been a disadvantage that even if a diversion occurs during the registration exposure, not only it is impossible to quantitatively detect the diversion but also even detection of the occurrence of the diversion is not possible.
Also, there has been a problem that the detection of a registration diversion between a wafer and a reticle is effected by forming reference patterns (e.g., vernier marks) of a test reticle on the wafer and measuring them with given measuring means, thus requiring much time and labor.